This application claims the priority of German patent document 100 56 573.5, filed 15 Nov. 2000 (15.11.2000), the disclosure of which is expressly incorporated by reference herein.
The invention relates to a transponder key for an electronic drive-away blocking device.
Currently, such a transponder key is widely used in vehicles together with a drive-away blocking device, such as is required by insurance companies. A transponder key may, for example, be a mechanical key with an integrated electronic unit for the code transmission or a purely electronic code card. Normally, the drive-away blocking device, having been activated after the ignition is switched off, is deactivated before the vehicle is started, by a coded exchange between the transponder key and a control unit inside the motor vehicle, to check authorization for a vehicle start. Thus, a cycle of the drive-away blocking device function starts with the deactivation status and ends with the activation status.
In the event of a theft, all approved keys must be presented to the insurance company, so that a theft as a result of a negligent handling of the keys can be excluded with reasonable probability.
One object of the invention is to provide an improved electronic drive-away blocking device of the mentioned initially type.
Another object of the invention is to provide a system which facilitates proof that a theft occurred despite care exercised by the vehicle owner.
Particularly in the case of vehicles with an electronic access system (transponder key) (also called “passive access” when no mechanical key is required), it should be possible to prove a proper handling/locking.
These and other objects and advantages are achieved according to the invention, in which a first memory area is provided in a transponder key for an electronic drive-away blocking device function, which may have at least a first status in the form of a deactivation of the drive-away blocking device and a second status in the form of an activation of the drive-away blocking device. Status information which indicates the respective last status can be stored in the memory area. More than two possible statuses may also be provided.
It is important that a cycle of statuses is provided which starts with the first status and ends with the second status. In this manner, when a transponder key is presented to the insurance company, if the second status is present as the (last) status information, it can be proven that the drive-away blocking device had been properly activated before the theft.
A second memory area is preferably also provided in the transponder key, in which a cycle counter information can be stored. The latter indicates the reading of a counter which will be incremented whenever a transition took place from the second status to the first status; thus, when a new cycle is starting.
Since normally more than one transponder key is assigned to a vehicle, it is possible that the drive-away blocking device can be deactivated, for example, by means of a first key and activated by means of another key. In this case, it can be checked by means of the cycle counter information whether at least the transponder with the highest counter reading has stored the second status as the last status.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
A transponder key 1 communicates, for example via radio transmission, with a drive-away blocking device control unit 2 on the inside of the motor vehicle. The drive-away blocking device control unit 2 is connected, for example, by way of a data bus with an engine control unit 3 for operating an internal-combustion engine. A code 4a is filed in the transponder key 1, and a code 4b is filed in the drive-away blocking device control unit 2.
In a representative embodiment of the invention, four statuses are defined:                a. first status: deactivation of the drive-away blocking device        b. second status: internal-combustion engine running        c. third status: internal-combustion engine stopped        d. fourth status: activation of the drive-way blocking device        
A cycle is: a-b-c-d.
The drive-away blocking device control unit 2 compares, for example, code 4a transmitted by the transponder key 1 with code 4b and deactivates the drive-away blocking device by a release signal to the engine control unit 3 when code 4a corresponds to code 4b (status information: a). Then the engine control unit 3 starts the operation of the internal-combustion engine. (Status information: b). After a drive, the ignition is switched off, for example, by the driver and the internal-combustion engine is stopped (status information: c). For example, after the withdrawal of the transponder key from the ignition lock (if provided), or after the removal of the transponder key 1 from the radio range, the driving-away blocking device is activated (status information: d). The cycle is terminated. During the next deactivation operation (status information: a), a counter is incremented. The cycle counter information X is therefore increased by one step X+1.
After a theft, at least the transponder key with the highest counter reading, when comparing the counter readings of all transponder keys approved for the vehicle (cycle counter information: Xmax,) has to contain d as the status information. In this manner, it can be proven that a theft occurred despite the proper activation of the drive-away blocking device, particularly in the case of passive-access vehicles.
The status information (a to d) and the cycle counter information (X, X+1 . . . ) can be formed either in the transponder key 1 itself or by the drive-away blocking device control unit 2. It is important that no later than after each activation of the drive-away blocking device, the two types of information are transmitted into the memory areas 5a (status information) and 5b (cycle counter information) of the transponder key 1.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.